This invention relates to the partial printing of a substrate with a plurality of layers to form a partially printed panel. Within each printed portion, at least one layer is applied to the substrate with inexact registration in relation to a second layer. A xe2x80x9ccontrol layerxe2x80x9d comprising xe2x80x9cedge sealing stripsxe2x80x9d is printed so that, within each printed portion, each edge of the at least two layers with inexact registration is located within the edges of an overlapping edge sealing strip. The edge sealing strips may provide a visual seal or mask at the edges of printed portions, for example to enable the each printed portion to have the desired color rendering that would otherwise not be consistently achieved through lack of registration. There are many other applications for the invention, for example to control any other incident wave characteristics of the partially printed panel, for example its solar radiation transmission, absorption and reflection characteristics. The invention can enable the physical sealing of printed portions containing gaseous or liquid fluids or particles in suspension, such as fragrances, or to produce printed portions to contain medication, for example skin patches with improved medication transfer control. Other applications of the invention include security printing, security labels, security seals and environmentally reactive labels, for example labels indicating the temperature regime to which a labeled product has been subjected.
There are a number of visual and other functional benefits in printing only part of the area of a substrate, some of which are outlined in GB 2 118 096 (Hill and Yule), GB 2 165 292 (Hill), PCT/GB96/02600 (Hill) and PCT/GB97/00020 (Hill).
Methods of partially printing a substrate with substantially exact registration of superimposed layers are outlined in GB 2 118 096, GB 2 165 292, GB 2 188 873, PCT/GB96/02600, PCT/GB97/02788 (Hill and Godden) and PCT/IB00/00267 (Hill and Clare). However, these methods typically involve the use of special inks and additional production stages compared to the simple deposition of layers of ink or other marking material. Partially printed substrates can typically be produced more economically by conventional methods of printing having inexact registration, providing any undesirable effects of such lack of registration can be consistently overcome.
PCT/GB96/02600 discloses why conventional printing processes all suffer inexact registration, owing to:
i) printing machine error or xe2x80x9ctolerancexe2x80x9d in delivering ink or other marking material,
ii) the dimensional instability of a liquid ink or other marking material in liquid state on a substrate,
iii) the dimensional instability of a substrate through temperature and humidity changes between printing xe2x80x9cpassesxe2x80x9d (printing of individual layers), and
iv) the error or xe2x80x9ctolerancexe2x80x9d in delivery of a substrate into the printing position.
Panels according to GB 2 165 292 cannot be reliably produced with conventional printing methods without special measures to overcome the otherwise inevitable color variance from that desired, both over the area of a single panel and between panels within a production run. Two such methods of creating acceptable panels by the management of conventionally printed layers are described in PCT/GB96/02600, referred to as the xe2x80x9cLateral Combination Methodxe2x80x9d and the xe2x80x9cThrough Combination Method.xe2x80x9d